installation - Ubuntu server 12.04 LTS USB install

I'm trying to install Ubuntu Server 12.04 from USB and I've been struggling with it for 3 days. I don't remember I had this hard time even when building my Hackintoshes.

So, now I'm at the point where I tried everything I found - Unetbootin, Startup disk creator, Live USB creator - nothing really works, as it doesn't detect the USB as a CD-ROM. I tried the switch cdrom-detect/try-usb=true to no avail. At least now I managed to get over this problem with the following method. I make the USB boot disk, I copy the *.iso to the USB too, I boot the installer and when I get the CD-ROM error, I ALT+F2 and do the following:

mkdir /usb
mount -t vfat /dev/sdb1 /usb
ls /usb (so I see the name of the ISO clearly)

mount -t iso9660 -o loop /usb/whatever-the-iso-is-called.iso /cdrom
ls /cdrom (so I see it has mounted the ISO right)

So mounting the ISO in a word. I select "Load configuration from CD-ROM" or something like that and I got rid of the CD-rom error. Everything's peachy until I get to the Configure APT screen, where it can't connect to the internet because I'm behind a firewall and it doesn't give me the choice to enter the proxy and it just quits to the installation choices screen. Now if I tell the installer to let me configure what software I want installed, it just tries to configure apt, it fails and it quits to the choices screen. Then I can continue the installation with install grub, it installs it and it works after restart.

BUT i have absolutely nothing installed, not even nano, my sources.list is empty with only the CD-ROM resources line. I don't know what to do... I need LAMP, SMB, SSL, CUPS installed - I don't want to do everything manually. Has anyone succeeded doing a start to finish installation using USB? If yes, how? BTW, everything works OK if you install from the CD (even if I plug the LAN cable out, it still configures apt and it still populates the sources.list). But I don't have a CD drive on the system I want to do the final install too and I don't want to buy any external CD drive just to get this done. All help welcome, I'm going crazy with this...

So I managed to do it, I'll write it down, maybe others confronting this problem will make use of it.

When you get to the point where because of the enterprise firewall the installer can't configure APT, just select the next step - Install GRUB and finish installation. Now you can boot in a bare bone ubuntu server. Leave the USB connected, reboot and login to the new server. Mount the *.iso again as your sources.list will contain only the ubuntu server CDROM as repo. Now, when that's done:

sudo apt-get install nano tasksel
sudo tasksel --list-tasks
sudo tasksel install what-ever-you-want-from-list

Now on with configuring the proxy:

sudo nano /etc/environment

and configure proxy there:

ex. http_proxy="http://192.168.X.X:PORT/"

Then go to http://repogen.simplylinux.ch and generate your sources.list, paste it through SSH or somehow, then:

sudo apt-get update

You're done.

EDIT: btw, I tried the USB install from home, without proxy and my experience is that the installer still fails to configure APT and System Clock. So you have to do the after-boot CD mounting anyway if installing from USB. Interestingly, using a normal CD works fine.